The present invention relates to vibratory devices of the type wherein blanks or parts and finishing media are introduced into a container which is vibrated for the purpose of surface treating the parts. Typical operations which are performed in this manner are: polishing or burnishing of metal; or cleaning, abrading and deburring of the surface of parts using abrasive finishing media placed in intimate contact with the parts.
In the case of conventional vibratory finishing devices, circular or elongate U-shaped bowls have generally been employed. When the bowl is vibrating, the parts and media travel in an orbital path along a generally horizontal plane. In a preferred arrangement, means are provided for receiving the parts and media during an upper portion of their travel to enable separation of the parts from the media and return of the media by gravity to the bowl for re-use. Finishing apparatus of the type described is illustrated in U.S. Pat. No. 3,693,298 to Ferrara; U.S. Pat. No. 3,100,088 to Podmore et al.; and U.S. Pat. No. 3,676,958 to Garland.
In such vibratory devices, very little relative motion between the media and parts occurs during certain portions of their travel together. The less the amount of relative movement between the media and parts, the longer it takes to complete the desired finishing operation. Another drawback of conventional vibratory equipment is their requirement to make use of media having a density within the range of 35 to 300 pounds per cubic foot. Since the metal surface removal rate is somewhat proportional to the weight and size of the media, such limitation on the media is undesirable.
Another type of prior vibratory device utilizes a bowl shaped container in which the parts and media are caused to move in a generally vertical plane. The movement is guided either by guide baffles or rotating arms within the bowl. Examples of such devices include U.S. Patent No. RE 27,084 to Balz and U.S. Pat. No. 3,611,638 to Deede. Such devices apply the vibrational energy to the parts from only one direction or require the use of a complicated rotating arm.
It is, accordingly, an object of the present invention to provide a vibrational method in which vibrational is applied energy to the media and parts throughout their entire travel through the device to maximize relative motion between the parts and media.
It is another object of the present invention to provide a vibratory method which has an increased material removal rate.
It is a further object of the present invention to provide a method which maintains the media and parts in pressure contact for increased material removal.
It is a still further object of the present invention to provide a method in which the parts can be accurately positioned in the media due to the continuous rotation of the media in helical, non-crossing paths.
It is a further object to provide a vibratory device which is not limited to the traditional range of media density.
It is a still further object to provide a method which is also capable of continuously scrubbing sand used in mold-making to remove the coating resulting from the molding process.
Other objects of the invention will become apparent from the concluding portion of the specification.